I am in Act 3 now with my team at lvl 62-56. I tackled Frozen Hearts which was a pain for so much time, but since I got the 9999+ dmg picto to start Act 3 and my parries were sound, it made going through the level so much easier. The Chromatic boss was surprisingly easy, too.
Right now I am trying out some of the 'Danger' areas, beating some previously tough Chromatic bosses and ticking off some of the trophy bosses and relationship levels. It may take a long time to reach lvl 80-85, which I need to be to tackle some tough bosses that have one/two-shotted me. I am really considering the Act 3 XP farm lol